Murder suspect will likely claim self-defense

John David Green, of Georgia, was extradited to Iowa last week to answer the charge for a 2009 killing

Sac County Attorney Ben Smith talks in a press conference this morning about the investigation and arrest of John David Green for the alleged murder of Mark Koster, of Sac City, in 2009. Green allegedly admitted that he choked Koster with a baseball bat.

Mark Koster

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April 1, 2014

SAC CITY

The man who allegedly admitted he killed Mark Koster in 2009 by striking him in the head and choking him with a wooden baseball bat - and then buried Koster's body in the dirt floor of a basement - will likely claim self-defense if the case goes to trial, Sac County Attorney Ben Smith said this morning in a press conference.

John David Green, 54, whom local and state law officers had tracked for about a year through four states, was arrested in Florida a week ago for first-degree murder after the admission to investigators.

Green and Koster, 58, were former co-workers at a Texas convenience store in the 1980s, Sac City Police Chief John Thomsen said this morning. Green had lived with Koster at Koster's Sac City house at 610 N. Fifth St. for about a month in the summer of 2009.

Green moved often and had a truck and camper in which he lived, Thomsen said.

Green alleges that Koster attacked him with the bat on June 5, 2009 - that he struck Green in the shoulder before Green took the bat and fought back.

"You don't have to be a rocket scientist or a lawyer (to know) that's maybe going to be something he raises as an affirmative defense," Smith said of the self-defense claim. "The state has a heavy burden of proof."

Smith declined to say what led to the 2009 altercation.

Koster was reported missing the next year and later declared dead by a Sac County jury.

A Carroll man, Lesly Gehlsen, 73, bought the house for $5,000 and discovered Koster's badly decomposed body in November 2012.

A state medical examiner found that Koster's neck bone and cartilage had been fractured, court documents show.

Smith said investigators identified Green as a possible suspect two months later, after they interviewed Koster's family and friends.

Police officers and state investigators - aided by officers in Kansas City, North Carolina, Georgia and Florida - tracked Green to Orange Park, Fla., where he was found gambling at a casino, Smith and Thomsen said. Court documents show Green was not currently employed and that he lived in Georgia.

Investigators also declined to say specifically how they tracked Green but called it "good old-fashioned police work" with the "best modern technology."

Smith expects to file formal charges against Green in district court this week of first-degree murder - which is punishable by up to life in prison ­- and obstruction of justice, because Green cleaned the alleged murder scene, concealed Koster's body and left a note that made it appear Koster had left town indefinitely.

Green allegedly said that he lived in Koster's house for a few days after he killed Koster and then went to Mississippi to visit his father.

Green was transported by police officers by airplane on Friday to Sac City, where he is held in the county jail. A judge denied him the opportunity to pay bail to be released and appointed an attorney, Charles Kenville, of Fort Dodge, to represent him. An assistant Iowa attorney general will assist with Green's prosecution, Smith said.